With the increasingly developed electronic industry, the electronic apparatuses, such as the Mobile Phone, the Personal Digital Assistant (PDA), the Notebook and the Planet Computer are developed toward the direction of being lighter, thinner, portable and multifunction. Nevertheless, as the electronic apparatus gets lighter and thinner, the development of the portability limits the size and capability of the battery of the electronic apparatus. Therefore, under the circumstance that the battery capability is limited, it becomes necessary to reduce the power consumption for increasing the battery life of the electronic apparatus.